<<Milk, especially the powdered variety significantly
weakens the gluten structure in proportion to the
amount used. >>
Don't get too concerned about this. There is a problem is using raw
milk in bread products. The active enzymes in the raw milk can affect
the structure of the bread and it can become quite gummy.
However, when milk is heated, these enzymes are deactivated and
cease to cause problems. This is why many (especially older) recipes
call for you to "scald" milk before using.
Generally, pasteurized milk has been sufficiently heated to eliminate the
problem. In 20 years of baking, I can remember only once, about 10 or
12 years ago, when I had this problem with pasteurized milk.
Raw milk is not commonly sold in most stores. A problem with a well-
known California dairy making a bunch of children some years back
has relegated raw milk to a hearty bunch of dedicated souls who are
willing to hunt it down. Such milk can be used in baking if the scalding
instructions are followed.
Given that powdered milk is made via heated deydration, I can't
imagine that you should have any problem with it in breadmaking.